This invention relates to cutting tools for making cylindrical bores and, more particularly, to a cutting tool for making cylindrical bores including two or more cutting inserts with radially or approximately radially directed blades which leave an uncut core, and chip removal devices extending in the axial direction of the tool.
Boring tools are known for providing bore holes of a fairly large boring depth in the case of which the boring depth ratio of the boring depth "L" to the bore hole diameter "D" amounts to approximately L:D&gt;5.
In the case of so-called deep-hole drilling, boring tools are used which, for the removal of boring chips, have a central chip removal duct inside a boring bar which is open in the direction of the boring advance.
For avoiding the hindering of the boring operation and damage to or destruction of the boring blades as well as damage to the bore wall, the removing of the boring chips and possibly of a boring core which remains uncut takes place by the feeding of a rinsing liquid between the bore hole wall and the boring blades of the tool.
The known German Patent Document DE-OS 23 16 762, for example, relates to such a boring tool. In this case, the discharge of the chips and possibly the discharge of a bore core which has remained uncut takes place by way of a central removal duct on the borer end or on the end of the boring bar carrying the boring tool.
The boring techniques applied by means of boring tools of the above-mentioned type require especially constructed machine tools with correspondingly adapted tool supports.
The present invention is based on known boring techniques whose advantageous method of operation consists of the fact that, during the boring, only a portion of the overall volume of the material must be cut while the central material portion in the form of a bore core which remains uncut is removed to the outside through the central duct of the boring bar. This reduces the boring power required for the boring and also considerably increases the tool life of the blades of the boring tool.
In comparison to the state of the art, it is the object of the invention to carry out, while using the known hollow drilling technique, the removal of the boring chips and of the bore core without the rinsing-in of liquid and without the use of machine tools of a special construction and not at the end of the boring bar of the boring tool.
This object is achieved by providing a cutting tool for making cylindrical bores including two or more cutting inserts with radially or approximately radially directed blades which leave an uncut core, and chip removal devices extending in the axial direction of the tool. The cutting tool is composed of at least two coaxial parts. One part forms the boring or cutting crown with the cutting inserts and the other part forms the support for the boring crown with a clamping shank. The chip removal devices extend axially along both parts and lead radially to the outside.
Because of the helical course of the chip removal ducts, the material which is cut during the boring operation, including the bore core which remains uncut, can be removed toward the rear and toward the outside without any impairment by the centrifugal forces occurring during the rotation of the boring tool and without the use of rinsing liquid.
The chip removal operation and the bore core removal is provided by the cutting inserts which are sloped with respect to one another and with respect to the longitudinal center plane of the tool.
As a result of the unimpaired removal of the cut material and of the bore core by way of lateral outlet openings of the removal ducts, perfect bore hole walls can be achieved.
The dividing of the boring tool into a cutting crown and a cutting crown support contributes to the fact that ducts of a relatively large width having a helical and radially outwardly directed course can be provided in the tool parts.
In addition, the tool is provided with a massive and stiff shank which can be clamped in with high radial forces by means of the normal clamping devices, such as three-jaw chucks, collet chucks, or the like.
Because of the removal of the cut material and of the bore core created during the boring operation by means of such tools through the chip removal openings in the radial direction, all chip removal machines with a separate drive that are customary in shops can use the tool according to the present invention.
An embodiment of a tool constructed according to the invention is illustrated in the drawing and will be described in detail by means of the following description.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.